Thanks for doing this. I prefer this mouse-over method to the other clicking and dragging ones.
Following on Liberation's suggestion, I've edited my Replacement text to remove the line break so I could embed multiple Spoiler tags in one paragraph, yet still alert the user to a Spoiler. It looks like this:
[Spoiler:] and spoiler stuff to follow on the same line.
Code:
<b>[<i>Spoiler:</i>]</b> <span class="spoiler" onmouseover="this.style.color='#FFFFFF';" onmouseout="this.style.color=this.style.backgroundColor='#000000'">Stuff goes here</span>
I've also attached an optional Icon to use with the Spoiler Tag.